Many portable electronic devices rely on one or more single-cell batteries for power. The plethora of different electronic devices, such as pagers, cellular phones, portable radios, portable CD players, flashlights, and other battery powered electronic equipment in use has created a great volume demand for single-cell battery power, resulting in the sale of both rechargeable and non-rechargeable single-cell batteries. The voltages and physical sizes of these batteries are standardized. For example, the AA 1.2-volt battery may be purchased as either rechargeable or non-rechargeable. Non-rechargeable single-cell batteries, such as AA 1.2-volt alkaline or carbon zinc batteries, are relatively expensive and need frequent replacement. The throw-away, or spent, batteries have themselves become an environmental concern, constituting hazardous waste.
Rechargeable batteries, such as nickel cadmium (NiCd) are available in conventional and identical sizes and substantially identical voltages as the non-rechargeable single cell batteries and are often used interchangeably with non-rechargeable batteries. The interchangeable use of either rechargeable or non-rechargeable small single cell batteries creates a problem for the user to distinguish between the rechargeable or non-rechargeable batteries, especially when dealing with a battery charger. To insert a non-rechargeable battery into a single cell battery charger creates a hazardous condition that can result in injury or damage due to leakage of chemicals from the non-rechargeable battery when recharging is accidentally attempted.
In the past, the battery charger itself or the battery would include a mechanical configuration to prevent the insertion or use of a nonrechargeable battery into the battery charger. Such mechanical configuration of either the battery charger or the battery adds additional expense to both components and the batteries of unique mechanical configuration are not readily available in stores. The present invention overcomes these problems by providing a battery charger that can, within seconds, electrically distinguish between a non-rechargeable and rechargeable single cell battery and charge only a rechargeable battery and stop charge to a non-rechargeable battery.